Stamped Concrete Structural Design
The structural design of a concrete patio is important for the longevity and the maintenance free aspects of stamped and colored concrete.
The strength of concrete is measured in psi (pounds per square inch) upon a compression test. The mix design for concrete patios in Minnesota should be at least 4000 psi.
2. Freeze/Thaw resistant
Because of the winters in Minnesota, an essential additive must be in all exterior concrete. The additive is air entrainment. Without air entrainment concrete will begin to flake and deteriorate after the first winter.
Concrete patios are poured at four inches thick.
All stamped and colored concrete must be reinforced with rebar. During the winter the sub-grade (ground) will freeze and move. Rebar keeps the concrete tightly held together throughout the freeze thaw cycle. Rebar prevents the control joints from opening up wide and keeps the slab sections level with each other. Unlimited Concrete Concepts’ standard rebar lay-out is every three feet each way in a grid fashion.
Fiber mesh is synthetic fiber strands distributed evenly throughout the thickness of the concrete slab. Fiber mesh is considered a secondary reinforcement (rebar is primary) and is not necessary in all concrete patio designs.
For stamped concrete, fibers may create an undesirable surface and are not recommended.
Sealer is required for all decorative concrete. The sealer brings out the colors and gives the stamped and colored concrete a finished look.
6. Base Material
A base material is only necessary when the subgrade is not uniform and uncompactable.
- Poor Soil
In most cases the sub-grade or base is not visual at the time of the estimate so an evaluation of the sub-grade is done once the old patio is removed. If the soil is poor and un-compactable, four to eight inches will need to be excavated and removed and a base material will need to be brought in. In this instance, a change order will be drafted and signed by all parties prior to work proceeding.
- Raise Elevation
In some instances the elevation of the patio needs to be raised. Base material will be brought in and compacted. This is determined at the time of the estimate.
- Enlarge or Extend
Many times new concrete patios are enlarged. Base material may need to be brought in to raise the elevation of the sub-grade or extend the base.